The present invention relates generally to bundling and attachment devices and more specifically to a tie for forming a plurality of elongate objects into a bundle and for holding a pair of objects together.
Plastic cable ties have become increasingly popular for a variety of bundling and attachment applications because of their relatively low initial cost and their ease of installation. For certain applications, however, it is more desirable to use a metallic tie. More specifically, plastic straps tend to become brittle when used at low temperature and have less desirable aging characteristics than comparable metal straps; e.g., when used in a high temperature, high humidity environment, plastic ties may undergo some elongation. Metal ties are also often preferably for underground installation and for use in corrosive environments. Additionally, plastic ties are inappropriate for certain nuclear powerplant applications since radiation can result in degradation of the plastic material thereby rendering the strap more brittle. Also, where it is desired to use the tie as a load carrying member, the metal tie is often preferable since it has much greater tensile strength.
Several self-locking bundling devices formed from metal have been proposed. In one type a plurality of regularly spaced vanes extend at an angle from the strap surface. During application, portions of the strap must be overlapped so that the vanes interleave. It will be appreciated that overlapping requires the use of a somewhat longer strap and metallic vanes extending from the strap could damage the insulation of wires in adjacent bundles. In another type of metallic tie the strap portion has a series of abutments which sequentially deflect a tongue in the locking head of the tie during threading. Examples of such ties are disclosed in U.S. Pat. Nos. 3,311,957, 3,694,863 and 3,964,133.
In one prior art bundling device a roller pin is used to wedge the strap against components of the locking head. Such a tie was relatively time consuming in use because it included several loose parts which required careful manual assembly. Additionally, it was possible to inadvertently release the strap because portions of the pin extended beyond the locking head. Reference may be made to U.S. Pat. No. 2,491,290.
In the nineteenth century metallic bundling devices incorporating locking balls were used for bundling bales of cotton or the like. Such devices had the disadvantage that they were not positively locking. That is, depending on the orientation of the locking head, gravity could hold the ball out of engagement with the locking ball resulting in release of the tightened strap. See, for example, U.S. Pat. Nos. 28,197 and 225,517.